This invention relates to a computerized three dimensional data acquisition apparatus and method for acquiring, inputting, and graphically displaying data concerning large three dimensional objects and spaces. More particularly, the invention relates to an apparatus and method for acquiring data directly from the physical objects and spaces, inputting the data to a computer aided drafting (CAD) program and graphically displaying the data as it is acquired to guide the input process and verify the results. In essence, the invention operates such that the user interfaces with the CAD program and uses the apparatus as an input device to enter data into the CAD program.
Computer models of three dimensional objects and spaces, such as building interiors and exteriors, accident scenes, and utility placements are used for many purposes. Building models are used as a source of information for real estate sales, leasing, and management. Architects use three dimensional computer models of buildings to optimize building layouts and to plan building renovations and remodeling among other things. Investigators use limited measurements and photographic means to record the overall context and disposition of the evidence at crime and accident scenes.
Computer models of buildings are usually derived from building plans. Unfortunately, the buildings as constructed often differ from their building plans. When an architect designs a building, he records the design on plans. The builder then uses the plans as a guide in the construction process. The builder, however, almost always constructs the building in a manner that varies at least slightly from the building plans. These variations are usually recorded on the building plans and the resultant corrected plans are called "as built" drawings. The builder generally measures the variations by hand and therefore the measurements are often inaccurate. Thus, the "as built" drawings provide general information on the variations from the building plans but they neither accurately portray the variations nor describe the variations in detail. Resultantly, the computer model is only as accurate as the plans or drawings. In the case of many buildings, plans do not even exist.
Frequently, then, the only way to create an accurate computer model of a building or any other large space is to physically measure the spatial characteristics of the building and to input the measured data manually into the computer program. In a normal procedure, a worker takes the measurements manually with a tape measure and later inputs the data into the computer. This technique also is slow and expensive and is even more prone to error than is creating a computer model from drawings.
Devices and methods have been disclosed for taking physical measurements in a manner that is more accurate and inexpensive than manually taking the measurements. For example, U.S. Pat. Ser. No. 4,295,201 to Wiklund discloses a device for fieldwise mapping an area. The device, in its preferred embodiment, is mounted on a tripod and comprises an electronic distance meter, a vertical angle unit, a horizontal angle unit that includes a detector that detects the earth's magnetic field, and a calculating unit. The device uses the earth's magnetic field to compute the distance from a fixed point to a measuring point on an object and the direction from the fixed point to the measuring point in the horizontal plane relative to a reference direction.
U.S. Pat. Ser. No. 4,205,385 to Ericson, et al. discloses a surveying system comprising a theodolite, a level sensor, and an on board microcomputer that can be used in conjunction with an electronic distance measuring instrument. The device translates raw data, comprising horizontal angle, vertical angle, and slope range, into the more useful component vectors, horizontal distance, latitude, departure, and elevation.
U.S. Pat. Ser. No. 5,091,869 to Ingram et al., discloses a method for creating a two dimensional floor plan of an existing building. The Ingram et al. device uses an electronic distance measuring device, a theodolite, and a data collector to measure the angles and distances to prominent points on the interior walls from an interior traverse point. The data collector stores the data for a later transfer to a separate computer. In a separate operation, the computer uses the data to create a two dimensional floor plan.
While the Ingram et al. method produces a floor plan of a building, it is only a variation of the traditional surveying methods as are used with the Ericson et. al system and the Wiklund instrument. Ingram et al. teaches a method for using surveying tools to survey the floor of a building. The data gathered by the method is primarily in the form of distances and angles which are only later converted to the cartesian coordinate system by a computer. However, the Ingram et al. method lacks the ability to generate an accurate three dimensional computer model, to graphically display the data as it is acquired, and to allow the user to interact with the CAD program during the data acquisition process.
A general area of technology, known as coordinate measuring machines (CMM) provides devices that digitize the precise geometry of discrete objects. The technology uses a short instrumented articulated arm with a stylus or a short range electronic distance measuring device (laser light or ultra-sound) that the user traces over the surface of the object. When prompted by the user, the device can record the location of the stylus' point or the electronic distance measuring device's range and transmit it to a computer for processing into a digital model of the object. In industry, the apparatus is fixed and is generally limited to use on relatively small discrete objects for proofing or copying the shape in the manufacturing process. Additionally, there are also some medical applications that use this type of device for precisely modeling parts of the body and similar objects.
Thus, there is a need in the art for a device and a method that overcomes these problems and limitations and that conveniently acquires data from and generates a three dimensional computer model of a large object or space, and that allows the user to view the information as it is acquired.